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Migrations Carol Wolf CS 396X. ISBNTitleAuthorImage 1234-5678EmmaAustenemma.jpg 2345-6789Oliver TwistDickenstwist.jpg 3456-7890HamletShakespearehamlet.jpg.

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Presentation on theme: "Migrations Carol Wolf CS 396X. ISBNTitleAuthorImage 1234-5678EmmaAustenemma.jpg 2345-6789Oliver TwistDickenstwist.jpg 3456-7890HamletShakespearehamlet.jpg."— Presentation transcript:

1 Migrations Carol Wolf CS 396X

2 ISBNTitleAuthorImage 1234-5678EmmaAustenemma.jpg 2345-6789Oliver TwistDickenstwist.jpg 3456-7890HamletShakespearehamlet.jpg Relational Databases  A relational database consists of a number of different tables.  Each table is like a two dimensional array.  The columns show the attributes (fields) of the data.  The rows each store information about a single item.  The first column stores the ISBNs for each book.  The first row stores information about Emma by Jane Austen.

3 Creating a table in Rails  InstantRails supplies an empty database called development.sqlite3.  A table is created by a migration. ruby script/generate scaffold book isbn:string author:string title:string  The resulting table will be called books and have the three columns named, above each holding a string.  It will also have several other columns supplied by Rails.  A primary key called id of type integer.  Timestamps of type date.  Rails gives the resulting Ruby program a name beginning with a timestamp, 20080805165427_create_books.rb.

4 Migration file to create a new table. class CreateBooks < ActiveRecord::Migration def self.up create_table :books do |t| t.string :isbn t.string :author t.string :title t.timestamps end def self.down drop_table :books end

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